DE102008059165A1 - Component with a catalytic surface, process for its preparation and use of this component - Google Patents

Abstract

The invention relates to a component with a catalyst surface (12). According to the invention, this surface (12) has metallic portions (14) and the former contacting portions of MnO 2 (13), the metallic portions preferably consisting of Ag and / or Ni. It has surprisingly been found that these material combinations achieve a greatly improved catalytic effect compared to the pure metals. In particular, when using the toxicologically acceptable Ni, these surfaces can be used, for example, in the air purification to reduce the ozone content. The surface can be applied for example by a coating (15) of the component, wherein the metallic portion and the proportion of MnO 2 in two layers (19, 20) is applied.

Description

The The invention relates to a component with a catalyst surface. Moreover, the invention relates to a method for manufacturing a catalyst surface on a component by cold gas spraying. Finally, the invention relates to a use of such a component.

A catalyst surface on a component is, for example, according to US 2003/0228414 A1 known. This catalyst surface can be produced by direct deposition of a catalytically active substance on the component. For this purpose, a cold gas spraying is used, in which the particles of the catalytic layer material are fed into a so-called cold gas jet, a process gas flowing at supersonic velocity. In the cold gas jet, these particles are accelerated toward the surface of the component to be coated and remain adhering to this surface while converting their kinetic energy.

The The object of the invention is to provide a component with a catalyst surface, a method for its preparation or a use of this Specify component, wherein the catalyst surface a should have comparatively high catalytic activity.

This invention is achieved with the aforementioned component or with a cold spraying process in that the catalyst surface consists of metallic portions and the first contacting portions of MnO ₂ . In order to produce such a layer, it is provided according to the invention that in the cold gas spraying the catalyst surface is produced by spraying MnO ₂ particles, wherein the MnO _{2 forms} only portions of the catalyst surface and also metallic portions of the catalyst surface are provided each adjacent to the shares of MnO ₂ . The metallic components can, as will be explained in more detail below, be provided by the metallic surface of the component to be coated or by admixing metallic particles in the cold gas jet.

By using MnO ₂ as a mating with a metal, it is possible according to the invention to achieve a particularly high catalytic activity of the catalyst surface formed. It has surprisingly been found that the catalytic activity of MnO ₂ , which is known per se, can be increased by metallic components on the surface, although overall the available catalytic surface of MnO _{2 is} reduced. This contradicts the expected result that a reduction of the real available surface area of MnO ₂ in the event of incomplete coverage of the surface of the component is accompanied by a proportional loss of catalyst activity.

This makes it advantageous to produce components with comparatively efficient catalyst surfaces by using portions of the catalyst surface instead of MnO ₂ with a metal. The surface of the component must therefore not be completely covered with the metallic components and the proportions of the MnO ₂ . It is sufficient already a partial coating to achieve the catalytic effect. Depending on the application, this is to be chosen so large that the available catalytic surface is sufficient for the desired effect for the conversion of ozone, for example. The proportion of MnO ₂ in relation to the total area formed by both fractions should be at least 10%, preferably 30 to 70%, in particular 50%.

According to an advantageous embodiment of the invention, it is provided that the MnO _{2 is present} at least partially in the γ-modification. The γ-modification is a structural constitution of the crystal formed by the MnO ₂ , which advantageously exhibits a particularly strong catalytic activity. However, the real structure of MnO ₂ is generally not exclusively in the γ-modification, but partly also in other modifications (eg the β-modification of MnO ₂ ). However, according to a particular embodiment of the invention, the microstructural content of MnO ₂ in the γ-modification should be more than 50% by weight.

According to another embodiment of the invention, it is provided that the component consists of the metal component making available metal and an only partially covering layer of MnO _{2 is} applied to this component. These are, for example, components made of Ag or Ni, which by virtue of their material composition already make available the one constituent required for the preparation of the catalytic surface. On these components, a production of the surface according to the invention is advantageously particularly easily possible by a non-covering layer of the other portion of the surface, namely MnO _{2 is} applied.

On the other hand, it is also conceivable that the component consists of a ceramic which provides the proportion of MnO ₂ and an only partially covering layer of the metal is applied to this component. For example, the component could be designed as a wear-stressed ceramic component. This does not have to consist exclusively of MnO ₂ . For example, it is conceivable that the ceramic as a sintered ceramic of different Species of particles is produced, wherein the MnO _{2 represents} a kind of these particles. However, it should be noted in this variant that the processing temperatures for the component must be below 535 ° C, since the MnO _{2 is} converted into MnO at this temperature and thus loses its excellent catalytic properties in the material combination according to the invention.

According to another embodiment of the invention it is provided that the component has a coating which provides the metallic components and the proportions of MnO _{2 of} the surface available. In this variant, components of various materials can be coated, wherein the catalytic properties of the layer according to the invention is advantageously caused solely by the nature of the layer or the catalytic surface formed by them. In this case, a suitable coating method must be selected in each case for the relevant material of the component.

As a method for producing the layer on the component, for example, a cold gas spraying can be used, wherein the catalytic surface is produced by spraying MnO ₂ particles. The MnO _{2 forms} only portions of the catalytic surface, the metallic components are formed for example by Ni and / or Ag. The metallic components can, as already described, either be provided by the component itself, or they are added as particles to the cold gas jet, so that the metallic components of the surface are formed by the layer that forms.

In particular, it is also possible to use MnO ₂ particles which at least partially exhibit the γ-modification of the MnO ₂ structure. In this case, the cold gas spraying with operating temperatures must be operated in any case below the decomposition temperature of the γ-modification. This temperature is 535 ° C. In terms of process, when choosing the temperature of the cold gas jet, a certain safety margin to this decomposition temperature can be maintained. On the other hand, it has been shown that a short-term exceeding of this temperature on impact of the MnO ₂ particles on the surface has no technical effect, because this temperature increase occurs extremely locally only in the surface region of the processed MnO ₂ particles. The particular core of the particles, which remains in an uncritical temperature range, can apparently stabilize the γ-modification of the particle structure sufficiently, so that the γ-modification of the MnO ₂ structure also remains on the catalytically active surface of the particles.

In addition, heating of MnO ₂ above 450 ° C results in conversion of MnO ₂ into Mn ₂ O ₃ . However, this process progresses only slowly, so that a short-term excess of the temperature, as occurs in cold gas spraying, is harmless.

In order to obtain the excellent catalytic properties of MnO ₂ , the γ modification of the microstructure must be at least partially contained in the MnO ₂ particles. This may be accomplished by a mixture of the MnO ₂ particles with manganese oxide particles of other modifications (e.g., β-modification of MnO ₂ ). Another possibility is that the particles consist of phase mixtures, so that the γ-modification of MnO _{2 is} not the only one present in the particles.

Furthermore, it is advantageous if nanoparticles with a diameter> 100 nm are processed as MnO ₂ particles. For the purposes of this invention, nanoparticles are understood as meaning particles which are <1 μm in diameter. It has surprisingly been found that such small particles of MnO ₂ can be deposited on the catalytic surface with a high degree of separation efficiency. Normally, on the other hand, it is assumed that particles of less than 5 μm can not be separated by cold gas spraying, since due to the low mass of these particles, the kinetic energy impressed by the cold gas jet is not sufficient for deposition. Why this is not the case for MnO ₂ particles in particular can not be explained exactly. Apparently, in addition to the effect of kinetic deformation, other adhesion mechanisms are involved in the film formation process.

The processing of nanoparticles of MnO ₂ has the advantage that with comparatively little material, a comparatively high specific surface and thus a strong expression of the catalytic effect can be achieved. Also, the boundary lines between the proportions of MnO ₂ and metallic portions of the catalytic surface are advantageously greatly extended in this way, which also affects a high degree of catalytic properties.

It is advantageous if a mixture of MnO ₂ particles and metallic particles for the metallic portions of the catalytic surface, so Ni and / or Ag, is used. In particular, by suitable choice of temperature and particle velocity in the cold gas jet, the energy input into the particles can then be controlled such that the specific (or inner) surface of the produced layer forming the catalytic surface is controlled. By a higher porosity of the layer produced, namely, the inner surface can be increased to an enlarged catalytic To provide surface. As a result, the germicidal effect can thus be increased. In contrast, it may also be advantageous if the surface is formed as smooth as possible in order to counteract a tendency to fouling.

In addition to the deposition by cold gas spraying, of course, other production methods are conceivable. For example, the catalytic surface can be produced electrochemically. In this case, the metallic portion of the catalytic surface is deposited as a layer electrochemically from an electrolyte in which particles of MnO _{2 are} suspended. These are then incorporated into the forming layer during the electrochemical deposition process and thus also form a fraction of MnO ₂ on the surface of the layer.

Another method can be obtained by preparing the layer from a ceramic containing at least MnO ₂ . For this purpose, a mixture of preceramic polymers, which form precursors of the desired ceramic, and metal particles in a solution can be applied to the component to be coated. First, the solvent is evaporated, then it can be converted to ceramic by a heat treatment, which is advantageously below the decomposition temperature of the γ-modification of MnO ₂ (535 ° C). Better still, the temperature remains below 450 ° C to prevent the formation of Mn ₂ O ₃ .

Among other things, the following embodiments of the component according to the invention can be produced using the methods mentioned. Thus, the coating produced can have a metallic layer on which an only partially covering layer of MnO _{2 is} applied. The metallic layer thus forms the metallic part of the surface that comes to light in the places where the layer of MnO ₂ does not cover. In this component design advantageously only a very small proportion of MnO _{2 is} necessary. It is also conceivable to use the above-mentioned manufacturing methods in combination. For example, the metallic layer can be produced galvanically and the only partially covering layer of MnO ₂ by cold gas spraying.

Another possibility is that the coating has a ceramic layer which provides the proportion of MnO ₂ and on which an only partially covering metallic layer is applied. This design of the component is of importance if the properties of the ceramic layer are structurally advantageous for the component (for example, corrosion protection).

It is also possible that the coating consists of a ceramic which provides the proportion of MnO ₂ and in which metallic particles are embedded. This is particularly advantageous if the ceramic layer is subject to wear and, as wear progresses, ie removal of the layer, it should retain its catalytic properties. The latter is ensured by the fact that again and again MnO ₂ particles are exposed during the removal of the ceramic layer, which ensure the proportion of MnO ₂ according to the invention on the surface. Of course, it is also conceivable that the layer has a metallic matrix in which the particles of MnO _{2 are} embedded. For this layer, too, the argument holds that the catalytic properties of a layer removal remain the same.

The component can also be designed such that this layer or a layer applied to it consists of a material which is different from the metallic component and from MnO ₂ and is present in this material (in the case of wear, see above) and / or on this particle in each case provide the metallic components and the proportions of MnO ₂ on their surface (meaning the surface of the particles). These are advantageously tailor-made particles with catalytic properties which can be applied universally to any surface or matrix. In each case, the method suitable for introduction or application must be selected. With this measure, for example, components made of plastic with catalytic properties can be produced. The particles introduced into the layer or component are either exposed to wear or, in the case of a porous structure of the component, can also be involved in the catalytic effect when they form the walls of the pores.

Last The invention relates to a use of the already described Component for reducing the ozone content of the catalyst surface sweeping Gas. This gas can primarily by the earth's atmosphere to provide. Under certain circumstances the air is enriched with ozone, z. On hot summer days in the inner city area or in higher atmospheric layers, which are used by air traffic. Because ozone harmful to health the human organism, the breathing air that comes from the Atmosphere in the interior of the vehicle or in the passenger cabin an aircraft is pumped by means of the catalyst surface according to the invention be largely freed from ozone. Of course Also applications in chemical engineering are conceivable.

The catalyst surface can, for example wise be configured as an inner lining of air-conducting piping systems. This has the advantage that by providing the catalyst surface no additional flow obstruction must be installed in the air-conducting channels. In order to increase the available catalyst surface, the air duct system can also be provided with an air-permeable insert, which must be flowed around by the sucked air.

Further Details of the invention are described below with reference to the drawing described. Same or corresponding drawing elements are provided in the individual figures with the same reference numerals and are explained only several times, as differences between the individual figures. Show it

the 1 to 5 different embodiments of the component according to the invention with different catalytic surfaces and

6 Measuring curves of the catalytic effect of an embodiment of the catalyst surface according to the invention in comparison to reference surfaces.

The 1 to 5 each show a component 11 with a surface 12 which has catalytic properties. These properties are created by the surface each having a share 13 which consists of MnO ₂ and continues to have a metallic content 14 made available from Ag or Ni. The component could be, for example, an air duct whose inner walls form the said surface.

The structure of the components 11 , which is shown in section, however, has differences. The component according to 1 itself consists of Ni or Ag, so its surface 12 automatically the metallic part 14 provides. On the surface 12 are still island-like areas of MnO ₂ formed, which is the proportion 13 provide. These can be applied, for example, as non-opaque coating by cold gas spraying.

According to 2 is a component 11 which consists of a material which is unsuitable for producing the catalytic properties of the surface. Therefore, attention is paid to this component 11 a metallic layer 15 made of Ni or Ag. On this layer, the proportion 14 provides MnO ₂ in the too 1 applied manner described, so that shares 13 arise.

In 3 is shown that the metallic layer also with particles 16 may be doped from MnO ₂ , ie, that these particles are in the metallic matrix 17 the metallic layer 15 are located. In this respect, they also form that part of the surface 12 that's the share 13 provides. The rest of the surface forms the share 14 ,

In 4 will the coating 15 through a ceramic matrix 21 formed, these pores 22 which has the inner surface compared to the outer surface 12 enlarge the component and thus also enhance a catalytic effect. In the ceramic matrix 21 are metallic particles 23 provided, both on the surface 12 the proportion 13 make available, as well as in the pores can be catalytically active. As with 2 and 3 can the component 11 according to 4 consist of any Ma material, with only the adhesion of the coating 15 on the component 11 must be ensured.

The component 11 according to 5 has a matrix of any material 24 , z. B. plastic. In this are particles 25 whose respective surface has both metallic components of Ni or Ag as well as fractions of MnO ₂ . In the embodiment according to 5 The particles themselves consist of the metal and the ceramic components are formed on the surface of the particles. Conceivable, of course, is the reverse case. The particles are on the surface 12 of the component 11 partially free, reducing the metallic content 14 and the shares 13 from MnO ₂ 13 be formed. Furthermore, there are shares 26 the surface 26 made of plastic, which are not catalytically active. The ratio of said proportions can directly by the degree of filling of particles 25 in the material 24 to be influenced.

In 6 the measurements are shown on a component with different catalytic surfaces. Here, the concentration of ozone in stationary flowing air is plotted on the Y-axis (unit ppb). The duration of the stationary flow is shown on the X-axis.

The content of ozone in the stationary air was between 980 and 1000 ppb, like the curve 30 can be seen. If a surface with proportions of Ag and Pd is used as the catalyst surface, the result is a curve 31 , It turns out that with a longer useful life, about 90% of the ozone contained in the stationary air could be broken down.

Furthermore, an in-plane sample of silver was used, which was completely covered with MnO (Ag was not the surface-forming portion, but only the material of the component). With this sample, the curve settled 32 It can be seen that the sample is degraded of 97% of the stationary air flowing in the ozone has settled.

With the catalyst surface of the invention, each half of the surface of Ag and half of MnO, can be compared to achieve a further improvement in the catalytic properties. The trace 33 shows that with this catalyst surface permanently more than 99% of the stationary air flowing in the ozone could be degraded.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• US 2003/0228414 A1 [0002]

Claims (19)

Component with a catalyst surface ( 12 ) characterized in that the catalyst surface ( 12 ) of metallic parts ( 14 ) and the former touching parts ( 13 ) consists of MnO ₂ . Component according to claim 1, characterized in that the manganese oxide is at least partially present in the γ-modification of MnO ₂ . Component according to claim 2, characterized that the microstructure present in the γ-modification of the manganese oxide is above 50% by weight. Component according to one of the preceding claims, characterized in that the surface portion of the portions ( 13 ) to MnO ₂ in relation to the sum of the metallic fractions ( 13 ) and the shares ( 13 ) at MnO _{2 is} at least 10%, preferably between 30 and 60% and in particular at 50%. Component according to one of the preceding claims, characterized in that the metallic component ( 13 ) consists of Ag and / or Ni. Component according to one of the preceding claims, characterized in that this from the metallic portion ( 13 ) is made available metal and an only partially covering layer of MnO _{2 is} applied to this component. Component according to one of claims 1 to 5, characterized in that this from a the proportion ( 13 ) consists of MnO _2- making ceramic and an only partially covering layer of the metal is applied to this component. Component according to one of claims 1 to 5, characterized in that this a coating ( 15 ), which the metallic components ( 14 ) and the shares ( 13 ) of MnO _{2 of} the catalyst surface ( 12 ). Component according to claim 8, characterized in that the coating ( 15 ) a metallic layer ( 19 ), on which a partially opaque layer ( 20 ) is applied from MnO ₂ . Component according to claim 8, characterized in that the coating ( 15 ) one the proportion ( 13 ) of MnO ₂ exhibiting ceramic layer, on which an only partially covering metallic layer is applied. Component according to claim 8, characterized in that the coating ( 15 ) from the proportion ( 13 ) of MnO ₂ ceramics, into the metallic particles ( 23 ) are embedded. Component according to claim 8, characterized in that the coating ( 15 ) of a metallic matrix ( 17 ), into the particles ( 16 ) are embedded from MnO ₂ . Component according to one of claims 1 to 5, characterized in that this or a layer applied to this from one of the metallic portion ( 14 ) and MnO ₂ different material ( 24 ) and in this and / or on this particle ( 25 ) are present, which in each case the metallic components ( 14 ) and the shares ( 13 ) of MnO ₂ at their surface. Method for producing a catalyst surface ( 12 ) on a component by cold gas spraying, characterized in that the catalyst surface ( 12 ) is produced by spraying MnO ₂ particles, wherein the MnO ₂ only shares ( 13 ) of the catalyst surface ( 12 ) and also a metallic component ( 14 ) are provided to the catalyst surface, each of which is assigned to the fractions ( 13 ) of MnO ₂ . A method according to claim 14, characterized in that MnO ₂ particles are used which at least partially have the γ-modification of the MnO ₂ structure and the cold gas spraying is operated at operating temperatures below the decomposition temperature of manganese oxide. Method according to one of claims 14 or 15, characterized in that are processed as MnO ₂ particles nanoparticles with a diameter> 100 nm. Method according to one of claims 14 to 16, characterized in that a mixture of MnO ₂ particles and metallic particles for the metallic portions ( 14 ) of the catalyst surface is used. Method according to one of claims 14 to 17, characterized in that the catalyst surface forming specific surface of the produced layer is controlled by the energy input into the cold gas jet. Use of a component according to a of claims 1 to 13 for reducing the ozone content one of the catalyst surface sweeping Gas.